/// CreateTime 2020/7/2 10:42
/// CreateUser chen 
/// ProjectName flutter_elf
import 'package:flutter_elf/config/component_index.dart';

import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';

enum IndicatorShape {
  //矩形
  rectangle,

  //圆角
  stadium,
}

/// Used with [TabBar.indicator] to draw a horizontal line below the
/// selected tab.
///
/// The selected tab underline is inset from the tab's boundary by [insets].
/// The [borderSide] defines the line's color and weight.
///
/// The [TabBar.indicatorSize] property can be used to define the indicator's
/// bounds in terms of its (centered) widget with [TabIndicatorSize.label],
/// or the entire tab with [TabIndicatorSize.tab].
class CustomUnderlineTabIndicator extends Decoration {
  /// Create an underline style selected tab indicator.
  ///
  /// The [borderSide] and [insets] arguments must not be null.
  const CustomUnderlineTabIndicator(
      {this.borderSide = const BorderSide(width: 2.0, color: Colors.white),
        this.insets = EdgeInsets.zero,
        this.gradient,
        this.margin,
        this.shape = IndicatorShape.rectangle,
        this.width})
      : assert(borderSide != null),
        assert(insets != null);

  final double width;
  final double margin;
  final IndicatorShape shape;
  final Gradient gradient;

  /// The color and weight of the horizontal line drawn below the selected tab.
  final BorderSide borderSide;

  /// Locates the selected tab's underline relative to the tab's boundary.
  ///
  /// The [TabBar.indicatorSize] property can be used to define the
  /// tab indicator's bounds in terms of its (centered) tab widget with
  /// [TabIndicatorSize.label], or the entire tab with [TabIndicatorSize.tab].
  final EdgeInsetsGeometry insets;

  @override
  Decoration lerpFrom(Decoration a, double t) {
    if (a is CustomUnderlineTabIndicator) {
      return CustomUnderlineTabIndicator(
        borderSide: BorderSide.lerp(a.borderSide, borderSide, t),
        insets: EdgeInsetsGeometry.lerp(a.insets, insets, t),
      );
    }
    return super.lerpFrom(a, t);
  }

  @override
  Decoration lerpTo(Decoration b, double t) {
    if (b is CustomUnderlineTabIndicator) {
      return CustomUnderlineTabIndicator(
        borderSide: BorderSide.lerp(borderSide, b.borderSide, t),
        insets: EdgeInsetsGeometry.lerp(insets, b.insets, t),
      );
    }
    return super.lerpTo(b, t);
  }

  @override
  _UnderlinePainter createBoxPainter([VoidCallback onChanged]) {
    return _UnderlinePainter(this, onChanged);
  }
}

class _UnderlinePainter extends BoxPainter {
  _UnderlinePainter(this.decoration, VoidCallback onChanged)
      : assert(decoration != null),
        super(onChanged);

  final CustomUnderlineTabIndicator decoration;

  BorderSide get borderSide => decoration.borderSide;

  EdgeInsetsGeometry get insets => decoration.insets;

  Rect _indicatorRectFor(Rect rect, TextDirection textDirection) {
    assert(rect != null);
    assert(textDirection != null);
    final Rect indicator = insets.resolve(textDirection).deflateRect(rect);
    return Rect.fromLTWH(
      indicator.left,
      indicator.bottom - borderSide.width,
      indicator.width,
      borderSide.width,
    );
  }

  @override
  void paint(Canvas canvas, Offset offset, ImageConfiguration configuration) {
    assert(configuration != null);
    assert(configuration.size != null);
    final Rect rect = offset & configuration.size;
    final TextDirection textDirection = configuration.textDirection;
    final Rect indicator = _indicatorRectFor(rect, textDirection).deflate(borderSide.width / 2.0);
    final Paint paint = borderSide.toPaint()..strokeCap = StrokeCap.square;

    //绘制渐变
    if (decoration.gradient != null) {
      paint.shader = decoration.gradient.createShader(rect);
    }

    //圆角角度
    final double radius = decoration.shape == IndicatorShape.rectangle ? 0 : borderSide.width / 2;

    double indicatorLeft, indicatorRight;
    if (decoration.width != null && decoration.width > 0) {
      //指示器一半宽度
      final indicatorWidth = decoration.width / 2;
      indicatorLeft = indicator.center.dx - indicatorWidth;
      indicatorRight = indicator.center.dx + indicatorWidth;
    } else {
      indicatorLeft = indicator.left;
      indicatorRight = indicator.right;
      if (decoration.margin != null) {
        indicatorLeft += decoration.margin;
        indicatorRight -= decoration.margin;
      }
    }
    final rrect = RRect.fromLTRBR(indicatorLeft, indicator.bottom - borderSide.width, indicatorRight,
        indicator.bottom, Radius.circular(radius));
    canvas.drawRRect(rrect, paint);
  }
}